Health benefits of tomatoes

Tomatoes are the edible fruits of the Solanum lycopersicum plant. They are believed to have originated from South America, precisely Ecuador and Peru (1). Today tomatoes are reported to be the most consumed vegetable in the world, with an average of 177.04 metric tons produced yearly worldwide (2).

Tomatoes are the most commonly grown vegetable here in the UK too, by home gardeners.

The most common tomatoes are the red tomatoes, though other varieties like scarlet, yellow, green, and even purple tomatoes exist. Besides, tomatoes vary in size with some as small as 1.5cm and others as large as 7.5cm. Moreover, they come in varying shapes like oval, elongated and pear-shaped.  They are popularly eaten raw in salads, used as an ingredient in different dishes or cooked principally as a sauce. Tomatoes can also be processed to canned tomatoes, tomato ketchup, purees, tomato juice or tomato paste (1).

Nutrition information

Tomatoes are very nutritious fruits, and a 100g serving of raw red ripe tomatoes has the following (3).

• Energy: 18 calories
• Water: 94%
• Protein: 0.9g
• Carbohydrate: 3.9g
• Fat: 0.2g
• Fiber: 2.8g
• Manganese: 0.3mg (13% DV)
• Potassium: 237mg (5% DV)
• Vitamin C: 13.7mg (16% DV)
• Vitamin K: 7.9µg (7% DV)
• Folate: 15µg (4%)

The DV (daily value) is reference amount of nutrient to consume daily or to not exceed daily. The percentage daily value (% DV) thus tells us how much a nutrient contributes to our diet per serving of the food or food product in question. A DV of 5% or lower is regarded as low, whereas a DV of 20% or above is considered high (4). 

Enhances vision

Tomatoes contain some naturally occurring colored pigments (carotenoids) called lutein and zeaxanthin. These are also referred to as macula pigments because they are the only two dietary carotenoids that accumulate in the macula of the eye’s retina.  Research studies have reported the delayed progression of eye diseases like cataracts and AMD (age-related macular degeneration) with lutein and zeaxanthin support therapy (5). 

Lutein and zeaxanthin protect the eyes from damage caused by blue light that comes from digital devices like computers and smartphones by absorbing these lights. Blue light has a short wavelength and is therefore very reactive and can trigger photooxidative degeneration (morphological and functional impairment of cells) in neurosensory layers of the retina (6).

Besides, they are strong antioxidants, and so they protect the macula of the eyes from oxidation reactions when the eyes are exposed to light. As antioxidants, they scout and free radicals which are responsible for the excessive oxidation reactions that cause oxidative stress and cell destruction (5).

Furthermore, lutein and zeaxanthin act as filters. They pre-filter blue light, inhibiting aberration and improving the contrast sensitivity of the things we look at. Thus, they increase the contrast of objects and their backgrounds which significantly improves vision (7).

Moreover, lutein and zeaxanthin have been demonstrated to ease headaches that result from eye strain and prevent eye tiredness (5).

Protects the skin from damage

Besides lutein and zeaxanthin, tomatoes also contain another carotenoid called lycopene. A 100g serving of raw ripe red tomatoes contains a significant 2570µg of lycopene (3). Lycopene is a potent antioxidant, reputed for its ability to protect the skin from photodamage (damage caused by sunlight). It scavenges oxygen free radicals that are unstable and cause excessive oxidation reactions. By so doing, lycopene reduces oxidative stress and the subsequent cell damage that results from it (8).

Lycopene also has the potential of preventing the generation of reactive oxygen species (free radicals), which are actively involved in oxidation reactions. Reactive oxygen species are extremely reactive molecules that are produced inside the body as byproducts of regular metabolic activities. They can also be generated from our diets and lifestyle activities. Fewer reactive oxygen species implies fewer oxidation reactions, and lesser cell damage that normally results from oxidative stress (9).

Oxidative stress causes chronic inflammation which can fragment collagen and disorganize the collagen fibers of the skin. This can aggravate skin pigmentation, skin aging (wrinkling), changes in the homogeneity of skin complexion and can even cause skin cancer (10). Collagen is the protein which is responsible for the elasticity and firmness of the skin. A decrease or decline in its concentration can significantly affect the structure, texture, and function of the skin (11).

Can help with blood clotting

Tomatoes are a rich source of the mineral manganese with a 100g serving providing for up to 13% of the daily value for manganese (3). Manganese is a vital mineral implicated in many essential biological processing like the formation of connective tissues, blood clotting factors, bones, and sex hormones. Manganese works collectively with vitamin K to ensure blood clots properly. When the body is wounded, blood clumps together and clots to form a natural scarf, that covers the wound to stop further bleeding. The blood vessels then open for a bit, to allow fresh nutrients as well as oxygen into the wound, facilitating healing (12).

Low levels of manganese can cause serious health conditions like bone malformation, infertility, body weakness and seizures (12).

Can protect the body from cancer

Lycopene present in tomatoes shows anti-cancer activities at several levels. It interferes with both the proliferation and migration of cancer cells in the body. It also suppresses the adhesion activities of cancer cells. Besides, lycopene has been proven to cause apoptosis (cell death) of cancer cells in several research studies (13).

The Mediterranean diet, which is a diet rich in fruits and vegetables, including tomatoes, accounts for the low cancer rates observed in that region of the world. Besides, several research studies have demonstrated lower risk for cancer with the regular consumption of tomato and tomatoes products (14).

In one study conducted in the US, the consumption of lycopene from different tomato products showed an inverse relationship with the risk of developing prostrate cancer. The results showed that consuming at least 10 servings of tomato products weekly showed a 35% reduction in the risk of developing prostate cancer (15). Another study showed that levels of lycopene in the serum and tissues had an inverse relationship with the risk for both breast cancer and prostate cancer (14).

Can reduce the risk for cardiovascular disease

Besides lycopene, tomatoes are also a good source of vitamin C which is another potent antioxidant. Antioxidants play an essential role in reducing the risk of cardiovascular disease by slowing down the progression of atherosclerosis (16). Atherosclerosis is the hardening or thickening of the arteries which results from the build up of plague (cholesterol, fatty substances, calcium, fibrin, and cellular wastes) (17).

The oxidation of low-density lipoproteins which transport cholesterol into the blood stream, is the main cause of atherosclerosis. So, antioxidants inhibit the oxidation of these low-density lipoproteins thus interrupting plague formation and consequently atherosclerosis (16).

In a study comparing different rates of death caused my coronary artery disease amongst Lithuanian and Swedish cohorts (of men aged 50 years), lower levels of blood lycopene were linked to an increased risk of death caused by coronary artery disease (18).

Can ease digestion

Tomatoes are a good source of both soluble and insoluble fiber, which helps to ease digestion of food. Soluble fiber dissolves in water forming a viscous gel that slows down the exit of food from the stomach. This can help keep a person feeling full for longer and can also aid with glucose control and absorption of nutrients is also slowed down. Insoluble fiber on the other hand draws water from the intestine, softens stool and makes it easier to pass out. It also increases bowel movements which helps to prevent constipation (19).

Fiber is not absorbed into the blood stream, so it reaches the large intestine intact, where it serves as food for healthy bacteria that live there. These feed on fiber and increase in number, phasing out disease causing bacteria and maintaining the integrity of the gut (19).

Manganese in tomatoes plays an important role in the breakdown of carbohydrates and fat as well as the absorption of calcium. Manganese deficiency can impair carbohydrate metabolism and insulin function which may offset glucose homeostasis (12).

Research studies have reported an association between low blood manganese levels and an increase in the prevalence of diabetes (20).

Strengthens the immune system

Tomatoes are good source of vitamin C, which is well known for its ability to boost the body’s immune system. It stimulates the production of lymphocytes and phagocytes, which are white blood cells involved in the first line of defense against disease causing bacteria. It facilitates the movement of these white blood cells to the area of infection and enables them to engulf and kill these bacteria (21).

Being a potent antioxidant, vitamin C also protects these white blood cells and other cells of our bodies from oxidation by free radicals. Oxidative stress breaks down the body’s immune tolerance, enhances chronic inflammation and cell death. Oxidative stress is implicated in the onset of many chronic diseases like cardiovascular disease, diabetes, cancer, and neurodegenerative diseases (like Alzheimer’s, dementia, and Parkinson’s disease) (21, 22).

Besides, vitamin C is a crucial part of the defense system of the skin, offering additional barrier against bacteria invasion of the body. Vitamin C stimulates the production of collagen, which the skin needs to maintain its strength, and elasticity. It is involved in the rapid healing of wounds, that is why people who suffer from vitamin C deficiency (called scurvy) experience slow healing of wounds, which can jeopardize the integrity of the body’s immune system (21).  

Can help lower cholesterol levels

Tomatoes contain a chemical substance called naringenin which has been proven to show cholesterol lowering activities in the body. It lowers the cholesterol production in the blood by decreasing the activity of the rate controlling enzyme, responsible for the production of cholesterol. Several research studies with animal models have demonstrated the effectiveness of naringenin intake in reducing blood cholesterol after as few as four weeks (23).

Another animal study carried out by the American Heart Association (AHA), showed that naringenin supplementation improved dyslipidemia (the imbalance of lipids like cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein. This resulted in a decrease in the progression of atherosclerosis (24).

Maintaining low levels of cholesterol is vital to reducing one’s risk for the development of cardiovascular disease. Besides containing no cholesterol, tomato consumption can help lower one’s blood cholesterol level (3, 23).

Can help lower blood pressure

The most abundant polyphenolic compound in tomatoes is called chlorogenic acid. It has been proven to significantly reduce both systolic and diastolic blood pressure in a couple of research studies (25). Chlorogenic acid works by triggering the effects of nitric oxide which is a potent vasodilator. Nitric oxide gas when produced, causes a widening of the blood vessels, which eases the flow of blood, consequently reducing blood pressure (26).

It is important to maintain a normal blood pressure, as it is vital to lower one’s risk for developing heart diseases. High blood pressure can damage the arteries of the heart and make them less elastic, which decreases the supply of blood and oxygen to the heart. High blood pressure can also cause heart failure, atrial fibrillation (abnormal heartbeat) and chronic kidney disease (27).

Tomatoes are super vegetables that are very nutritious and readily available and affordable. Thus, consuming tomatoes regularly is doable and since their applications are so varied, consuming them in different styles and forms is also very achievable.

However, it should be noted that tomatoes may trigger heart burns for people suffering from acid reflux or GERD (gastroesophageal reflux disease). This is because tomato is an acidic fruit with a sour taste, and so when eaten raw can trigger the production of stomach acids, that can trigger the backflow of acid and heartburn sensation. So sensitive people should be careful with the consumption of tomato and tomato products like ketchup, pastes, purees, and juices (28).

Also, some people may experience allergic reactions upon eating tomatoes. This allergy is linked to grass pollen and latex allergies. Symptoms could be mainly oral, occurring at the mucosa of the lips, tongue, or pharynx after consumption. Symptoms could also cause some reactions at the level of the digestive tract or cardiovascular system (29).

Furthermore, tomatoes naturally contain high amounts of histamine, which is well known for its role in triggering allergic and anaphylactic symptoms. So, people with histamine intolerance may experience symptoms upon consumption of tomatoes or its products (30).

REFERENCES

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